Microsoft finally fixed the 2GB PST limit in Outlook 2003 and newer.

The PST files usually aren't actually corrupted when they hit 2GB. Its just that Outlook can't load them once they get past that point so you're kinda stuck. You have to truncate the file, use one of the many recovery tools or upgrade it to the newer can-cope-with-2GB-and-above PST format in Outlook 2003.

For long term mail storage, you should convert it to a text based format or something. I guess mbox would be okay if its just an archive.